This invention relates to a dimmer switch system, and more specifically relates to a novel dimmer switch which can be used in combination with multiple-location remote switching devices.
Switching devices which are operable from a plurality of locations to cause switching of a given incandescent lamp load are well known. Such devices commonly employ combinations of three-way and four-way switches which are connected in series with one another such that the operation of any of the switches will reverse the energization state of the load between an on or off state. Dimmer structures may be connected in series with the switching circuit. Devices of this type are sold, for example, by the Lutron Electronics Co., Inc., the assignee of the present invention under the trademark "Skylark". The dimming structure may be combined with a series single pole, double throw switch and the assembly is adapted to be mounted on a wall box. A linearly movable slide is provided for adjusting the dimming power level. Individual series connected three-way and four-way switches may then be used with this assembly to provide for remote turn-on and turn-off of the load.
In switching systems of this type, there is provided single location dimming with multiple location switching. However, all switch contacts at all locations must be rated to carry full load current and, moreover, all wiring must be rated to carry full load current. For example, No. 12 wire is commonly used for installations which carry from 15 to 20 amperes load current. Also, a minimum of three wires is required at each remote switch location.
A second multiple location switching and dimming system is known which employs a plurality of remotely located touch plates at a plurality of respective remote locations. Each of the touch plates will control turn-on or turn-off of a common dimming circuit and will control the dimming level. Devices of this type have numerous disadvantages. For example, they require bare skin contact with the touch plates for actuation of the dimmer circuit. Moreover, there is no tactile feedback upon actuation. Another disadvantage of these systems is the need to wait for a given light level to be reached when changing from one level to another. Also, there is no indication of the light level setting when the lights are off. Such systems are also sensitive to a-c wiring polarity and loss of the previous on/off status and dimming level if the a-c supply fails. There also appears to be a limit on the number of touch plates which can be used in a given system and a limit to the distance between the touch plates and the main dimmer circuit. A serious disadvantage of such systems is that the touch plate wiring cannot be near load wiring so that existing three-way wiring in a residential or commercial installation cannot be used for the touch plate system.
Low voltage latching relay switching systems are known, which use momentary contact push buttons to energize or deenergize a latching power relay which switches the load current. This system requires three wires to each control location, plus a separate power supply and latching relay.